docs: def trace_roi(hemi, map_proj, closed=True, event_handlers=None, alternate_plots=None, **kw):
      '''
      trace_roi(hemi, map_proj) yields an ROIDrawer object that controls the tracing of lines around
        an ROI in a 2D matplotlib plot. After the ROI has been drawn in the plot, the resulting path
        trace can be obtained via the roi_drawer.trace object.
  
      ROI tracing is very simple: any point in the plot is appended to the path as it is clicked; in
      order to eliminate the previous point, hold shift while clicking. To end the path, hold control
      while clicking. To abort the path, hold both shift and control while clicking. (Double-clicking
      should be equivalent to control-clicking, but this does not work in all setups.) In order to use
      the ROI tracing, `%matplotlib notebook` is recommended.
  
      The trace_roi() function accepts all options that can be passed to cortex_plot() as well as the
      following options:
        * closed (default: True) specifies whether the path-trace that is constructed should be closed
          (True) or open (False).
        * event_handlers (default: None) specifies additional event handlers (named by key) for the
          ROIDrawer().
        * alternate_plots (default: None) specifies a list of alternate plotting functions that must
          accept the axes as an argument (these are cycled with tab-click). Alternately, these may be
          matplotlib TriMesh objects that are simply made visible.
      '''
      if event_handlers is None: event_handlers = {}
      if alternate_plots is None: alternate_plots = []
      # if if there are alternate plots, go ahead and set them up:
      if alternate_plots:
          pass